[add] support for RTL layout

Add `I18nManager` API from React Native. This can be used to control
when the app displays in RTL mode.

Add `$noI18n` property suffix for properties that StyleSheet will
automatically flip. This can be used to opt-out of automatic flipping on
a per-declaration basis.

docs/components/Text.md

@@ -68,14 +68,22 @@ Lets the user select the text.
 + `fontWeight`
 + `letterSpacing`
 + `lineHeight`
-+ `textAlign`
++ `textAlign`‡
 + `textAlignVertical`
 + `textDecorationLine`
-+ `textShadow`
++ `textOverflow`
++ `textRendering`
++ `textShadowColor`
++ `textShadowOffset`‡
++ `textShadowRadius`
 + `textTransform`
++ `unicodeBidi`
 + `whiteSpace`
 + `wordWrap`
-+ `writingDirection`
++ `writingDirection`‡
+
+‡ This property can be suffixed with `$noI18n` to prevent automatic
+bidi-flipping in RTL mode. This is only supported if `Platform.OS === 'web'`.
 
 **testID**: string